WordPress at a glance
class is not described

WP_Http_Encoding{} WP 2.8.0

Core class used to implement deflate and gzip transfer encoding support for HTTP requests.

Includes RFC 1950, RFC 1951, and RFC 1952.

Hooks from the class
Return

null. Null. Nothing.

Usage

$WP_Http_Encoding = new WP_Http_Encoding();
// use class methods

Methods

  1. accept_encoding( $url, $args )
  2. compatible_gzinflate( $gzData )
  3. compress( $raw, $level = 9, $supports = null )
  4. content_encoding()
  5. decompress( $compressed, $length = null )
  6. is_available()
  7. should_decode( $headers )

Changelog

Since 2.8.0 Introduced.

Code of WP_Http_Encoding{} WP 5.7

<?php
class WP_Http_Encoding {

	/**
	 * Compress raw string using the deflate format.
	 *
	 * Supports the RFC 1951 standard.
	 *
	 * @since 2.8.0
	 *
	 * @param string $raw      String to compress.
	 * @param int    $level    Optional. Compression level, 9 is highest. Default 9.
	 * @param string $supports Optional, not used. When implemented it will choose
	 *                         the right compression based on what the server supports.
	 * @return string|false Compressed string on success, false on failure.
	 */
	public static function compress( $raw, $level = 9, $supports = null ) {
		return gzdeflate( $raw, $level );
	}

	/**
	 * Decompression of deflated string.
	 *
	 * Will attempt to decompress using the RFC 1950 standard, and if that fails
	 * then the RFC 1951 standard deflate will be attempted. Finally, the RFC
	 * 1952 standard gzip decode will be attempted. If all fail, then the
	 * original compressed string will be returned.
	 *
	 * @since 2.8.0
	 *
	 * @param string $compressed String to decompress.
	 * @param int    $length     The optional length of the compressed data.
	 * @return string|false Decompressed string on success, false on failure.
	 */
	public static function decompress( $compressed, $length = null ) {

		if ( empty( $compressed ) ) {
			return $compressed;
		}

		$decompressed = @gzinflate( $compressed );
		if ( false !== $decompressed ) {
			return $decompressed;
		}

		$decompressed = self::compatible_gzinflate( $compressed );
		if ( false !== $decompressed ) {
			return $decompressed;
		}

		$decompressed = @gzuncompress( $compressed );
		if ( false !== $decompressed ) {
			return $decompressed;
		}

		if ( function_exists( 'gzdecode' ) ) {
			$decompressed = @gzdecode( $compressed );

			if ( false !== $decompressed ) {
				return $decompressed;
			}
		}

		return $compressed;
	}

	/**
	 * Decompression of deflated string while staying compatible with the majority of servers.
	 *
	 * Certain Servers will return deflated data with headers which PHP's gzinflate()
	 * function cannot handle out of the box. The following function has been created from
	 * various snippets on the gzinflate() PHP documentation.
	 *
	 * Warning: Magic numbers within. Due to the potential different formats that the compressed
	 * data may be returned in, some "magic offsets" are needed to ensure proper decompression
	 * takes place. For a simple progmatic way to determine the magic offset in use, see:
	 * https://core.trac.wordpress.org/ticket/18273
	 *
	 * @since 2.8.1
	 *
	 * @link https://core.trac.wordpress.org/ticket/18273
	 * @link https://www.php.net/manual/en/function.gzinflate.php#70875
	 * @link https://www.php.net/manual/en/function.gzinflate.php#77336
	 *
	 * @param string $gzData String to decompress.
	 * @return string|false Decompressed string on success, false on failure.
	 */
	public static function compatible_gzinflate( $gzData ) {

		// Compressed data might contain a full header, if so strip it for gzinflate().
		if ( "\x1f\x8b\x08" === substr( $gzData, 0, 3 ) ) {
			$i   = 10;
			$flg = ord( substr( $gzData, 3, 1 ) );
			if ( $flg > 0 ) {
				if ( $flg & 4 ) {
					list($xlen) = unpack( 'v', substr( $gzData, $i, 2 ) );
					$i          = $i + 2 + $xlen;
				}
				if ( $flg & 8 ) {
					$i = strpos( $gzData, "\0", $i ) + 1;
				}
				if ( $flg & 16 ) {
					$i = strpos( $gzData, "\0", $i ) + 1;
				}
				if ( $flg & 2 ) {
					$i = $i + 2;
				}
			}
			$decompressed = @gzinflate( substr( $gzData, $i, -8 ) );
			if ( false !== $decompressed ) {
				return $decompressed;
			}
		}

		// Compressed data from java.util.zip.Deflater amongst others.
		$decompressed = @gzinflate( substr( $gzData, 2 ) );
		if ( false !== $decompressed ) {
			return $decompressed;
		}

		return false;
	}

	/**
	 * What encoding types to accept and their priority values.
	 *
	 * @since 2.8.0
	 *
	 * @param string $url
	 * @param array  $args
	 * @return string Types of encoding to accept.
	 */
	public static function accept_encoding( $url, $args ) {
		$type                = array();
		$compression_enabled = self::is_available();

		if ( ! $args['decompress'] ) { // Decompression specifically disabled.
			$compression_enabled = false;
		} elseif ( $args['stream'] ) { // Disable when streaming to file.
			$compression_enabled = false;
		} elseif ( isset( $args['limit_response_size'] ) ) { // If only partial content is being requested, we won't be able to decompress it.
			$compression_enabled = false;
		}

		if ( $compression_enabled ) {
			if ( function_exists( 'gzinflate' ) ) {
				$type[] = 'deflate;q=1.0';
			}

			if ( function_exists( 'gzuncompress' ) ) {
				$type[] = 'compress;q=0.5';
			}

			if ( function_exists( 'gzdecode' ) ) {
				$type[] = 'gzip;q=0.5';
			}
		}

		/**
		 * Filters the allowed encoding types.
		 *
		 * @since 3.6.0
		 *
		 * @param string[] $type Array of what encoding types to accept and their priority values.
		 * @param string   $url  URL of the HTTP request.
		 * @param array    $args HTTP request arguments.
		 */
		$type = apply_filters( 'wp_http_accept_encoding', $type, $url, $args );

		return implode( ', ', $type );
	}

	/**
	 * What encoding the content used when it was compressed to send in the headers.
	 *
	 * @since 2.8.0
	 *
	 * @return string Content-Encoding string to send in the header.
	 */
	public static function content_encoding() {
		return 'deflate';
	}

	/**
	 * Whether the content be decoded based on the headers.
	 *
	 * @since 2.8.0
	 *
	 * @param array|string $headers All of the available headers.
	 * @return bool
	 */
	public static function should_decode( $headers ) {
		if ( is_array( $headers ) ) {
			if ( array_key_exists( 'content-encoding', $headers ) && ! empty( $headers['content-encoding'] ) ) {
				return true;
			}
		} elseif ( is_string( $headers ) ) {
			return ( stripos( $headers, 'content-encoding:' ) !== false );
		}

		return false;
	}

	/**
	 * Whether decompression and compression are supported by the PHP version.
	 *
	 * Each function is tested instead of checking for the zlib extension, to
	 * ensure that the functions all exist in the PHP version and aren't
	 * disabled.
	 *
	 * @since 2.8.0
	 *
	 * @return bool
	 */
	public static function is_available() {
		return ( function_exists( 'gzuncompress' ) || function_exists( 'gzdeflate' ) || function_exists( 'gzinflate' ) );
	}
}